This scene took ages to tape. They didn't want to have William Shatner flattened by a car so all the cars in the scene were driven by the crew. They all had to be at the right place at the right time and getting them all in position in heavy San Francisco traffic took at least twenty minutes, and they had to reshoot the scene quite a few times. With 20-30 minutes between each shooting, it took over three hours before they finally got it right.